The present invention relates to a pneumatic tire having a contoured zone in each sidewall. Pneumatic tires are laminated mechanical devices of generally toroidal shape having beads and a tread. In particular, the pneumatic tire of the present invention is a radial-ply tire. The term "radial-ply" tire is intended to include a belted or circumferentially restricted pneumatic tire in which the ply cords which extend from bead to bead are laid at cord angles between 65.degree. and 90.degree. with respect to the equatorial plane of the tire.
Radial truck tires are prone to have circumferential ply-breaks in the ply sidewall region under certain operation conditions. Such conditions include a dual tire running at zero or low inflation pressures while the tire is being used as one of a tandem set of tires, typically on a 18 wheeled vehicle. While this is not the recommended mode of usage of the tire, it is a rather common practice. This situation weakens the ply to the extent of breakage, or causes a loss in fatigue resistance and/or ultimate strength in the ply at the sidewalls so that blow-out may occur upon subsequent re-inflation of the tire. Therefore, there exists a need to compensate for this common but unrecommended occurrence in radial tires.